- Histologically proven infiltrating carcinoma of the breast on core needle biopsy that is: ER/PR ≤10% staining by IHC and HER2 positive - IHC 3+, ISH ≥2.0, or average HER2 copy number ≥6.0 signals per cell or per current ASCO-CAP (American Society of Clinical Oncology - College of American Pathologists) or NCCN (National Comprehensive Cancer Network) guidelines. Note: All histological diagnostic material should be reviewed at enrolling institution as required per local standards.